convergence problems when melting SiC at high pressure

[Fernan Saiz]

Hello,
I am studying the melting of a 256-atom SiC system at high pressures using 
the Z-method. I face the problem that when the pressure is around 10 o 20 
GPa (obtained by reducing 1% the simulation cell size), the ab-initio 
molecular dynamics at NVE does not converge after several hundred steps. I 
tried reducing the timestep to 0.05 fs with a cutoff of 800 Ry for an 
initial temperature of 9000 K, which after a few hundred steps goes down to 
to some 4000 K and the system starts to melt. However, this system does not 
converge even though I used the CG minimizer with a eps_max 1.0E-6 for the 
inner and outer loops, the preconditioner FULL_ALL with the PADE 
functional. Input script file is attached.

I was wondering if I could receive any useful piece of advice.

Best regards,
 - Fernan Saiz
Department of chemistry
Imperial College London
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